Sonnen has good "defensive striking". By that I mean he usually doesn't do much damage to his opponents but they can't do anything to him either because he shuts down their offense. It's kinda similar to Khabib's striking,on paper it looks a bit choppy and weak yet no one was able to really outpoint or outstrike him in 26 fights (he got hit by Johnson a couple of times and that's it). Chael was knocked down like twice in his entire career and he has been fighting since 1997 so his stand up abilities are underrated.
I think that Fedor can knock him out but I won't bet on it. I actually think Fedor might have better chances to finish this fight if he takes Chael down himself. That's where Chael is proven to be bad,his ground game off the back is pitiful. He doesn't like to get put in that position and covers up like a turtle (Jones,Rashad,Tito,Maia and some other fights). I'd pick Fedor over Chael 65% to 35%,which means that he is a favourite overall but I won't be surprised if he loses